Pneumatic hammer



Filed Aug. 18, 1947 INVENTOR. ./Ac/r E. Tlf-,eey BY yy, f90/QCM@ 7"TOENEVS Patented Feb. 19, 1952 PN EUMATIC HAMMER Jack E. Terry, NorthRoyalton, Ohio, assignor,

by mesne assignments, to The Bingham-Herbrand Corporation, Toledo, Ohio,a corporation of Ohio Application August 18, 1947, Serial No. 769,132

Z Claims. 1

The present invention relates to a pneumatic hammer and moreparticularly to a pneumatic hammer of a type which may be manipulated byone hand of the operator.

An object of the invention is to provide a pneumatically operated hammerin which the hammer is operated with a maximum of efficiency and inwhich the air is exhausted from the hammer in such a manner thatpractically all cushioning of the hammer due to building up ofunexhausted air is eliminated.

Another object of the invention is to provide a pneumatic hammer inwhich the hammer reciprocates in a cylinder freely outwardly of thecylinder to deliver the hammer blow but which is checked on the inwardstroke by an air cushion to prevent striking the inner end of thecylinder.

Other objects and advantages of the invention will be apparent from thefollowing description of a preferred form of the invention, referencebeing made to the accompanying drawings wherein:

Fig. 1 is a view in section of a pneumatic hammer;

Fig. 2 is a View similar to that of Fig. 1 but showing certain parts ofthe hammer piston in different positions;

Fig. 3 is a view in section taken on line 3 3 of the drawings;

Fig. 4 is a view in section taken on line 4-4 I have shown it in theformrof an air` powered hammer indicated generally at 5, which hammermay be of a size to be readily manipulated by one hand of the operator.The hammer consists of a handle member 5, which may be made of anysuitable material such as cast aluminum and it is formed similar to wellknown pistol type grips. The upper part of the handle is bored asindicated at "I, and the bore is threaded internally as indicated at 8.A barrel member I!) is threaded into the bore, and this member I 5 ispreferably made of a heat treated steel and it includes an axial boreextending therethrough and the bore-*has three sections of diierentdiameters. The first section of the bore having the smallest diameter asindicated at I2 and this section is adapted to accommodate a tool memberI3, which may be a chisel, or peening tool, for example, and which isadapted to reciprocate in this section. Preferably, the bore is breachedto form a haxagonal cross section so that the tool may be of hexagonalstock to prevent rotation thereof. The

second or intermediate section of the bore is indicated at I3 and thethird section is indicated at I4. Mounted in the sections I3 and I4 ofthe bore in the barrel is a hammer piston I5 which includes a shankportion i6 and a head Il. The shank portion closely fits the walls ofthe section I3 of the bore and the head I'I closely fits the walls ofthe section I4 of the bore. It will be noted that an annular shoulder I3will be formed by the head Il. This hammer piston is adapted to bereciprocated by air pressure, in a manner to be described hereinafter,and it strikes the inner end of the tool 4i) to impart a hammer blow tothe tool.

The piston l5 is adapted to strike the tool di) as it is moved to theleft and the tool is mounted in the section I2 of the bore in the barrelmember so that it may have a limited longitudinal freedom of movement.This is accomplished by forming a wide groove 32 in the tool andproviding two opposed ball members 33 in tapered openings 34 in thebarrel member, which ball members may partially project into the groove32 for cooperating with the edges of the groove to limit thelongitudinal movement of the tool. The ball members 33 may be retainedin this position by a collar 35 surrounding the barrel member. Thecollar is provided with detents on opposite sides, which detents whenaligned with the balls 33 will permit the balls to recede in theopenings 34 to unlock the tool to permit its insertion or removal fromthe barrel. The collar 35 is maintained in place by a split ring 38 andit is normally retained in tool locking position by a detent ball 39.

The piston I5 has an axial bore 2t therein which opens in the end of thepiston head I I facing the end of the cylinder formed by the bores inthe barrel member and the handle inember, part of which cylinder is thesection It of the bore in the barrel member. The bore 2Q terminatoswithin the shank portion of the piston and two tapered ports 2! leadradially from the bore 'le and open in the side surfaces of the shank.

An annular groove 22 is formed about the interior of the barrel memberand in the section i3 of the bore of the barrel member, and the grooveis located so that it will be aligned with the ports 2l when 'the pistonI5 is in the left hand extremity of its stroke, as viewed in Fig. 1.'I'hree outlet passages 23 are drilled through the barrel member forforming an outlet from the groove 22, which outlets lead to theatmosphere. When the piston I5 is at the opposite extremity of itsstroke as shown in Fig. 2, the ports 2| will be positioned at the lefthand end of the cylinder formed by the section I4 of the barrel member.Preferably, two opposed passages 24 are formed in the barrel member andlead from section I3 of the bore to permit breathing when the hammerpiston reciprocates.

Air under pressure is fed into the bore I through a port'25, which portis located remote from the closedend of the cylinder in which the pistonhead operates and adjacent to the end of the cylinder which communicateswith the section I3 of the bore in the barrel member'. Air is fed to theport 25 through drilled passages 26, 21 and 28 in the handle member 6,and a finger actuated valve mechanism is disposed intermediate passages26 and 21 for controlling the ow of air through the passages. This valvemechanism is described in my co-pending application, Serial No. 780,633,led `October 18, 1947, although it may be of any suitable type, many ofwhich are Well known in the art. Therefore, the valve will not bedescribed in detail here as it forms no novel part of this invention.

When the valve 29 is open, air will enter the bore I4 through port 25and when the piston I1 is in the position shown in Fig. 1, the pressureagainst shoulder I8 Will force the piston to the right until ports 2|enter into the cylinder I4. At this time the air will then enter ports2i, pass through the bore 20 and into the end of the cylinder I4 Whereit will cause piston I5 to be rapidly propelled to the left. As thepiston moves to the left, bores 2l are momentarily closed by the Wallsof the section I3 of the bore in the barrel member until these bores arebrought in registration wth the groove 22 at which time the air will beexhausted from the piston through the groove 22 and out the outlets 23.When the air is thus exhausted the piston will move to the right againas described.

I have found that by providing the annular groove 22 in the bore of thebarrel member air is exhausted from the piston more efficiently than ifthe groove would be formed in the piston as has been the practice in thepast. Furthermore, I have found that the ratio of the volume f of thebore 2D to the volume of the annular groove 22 materially affects theeiciency of operation of the piston as a hammer and that this ratio isquite critical. I have found that the volume of the annular groove 22should be 1.65 times the volume of the bore 2G in the piston and thatthis ratio must be adhered to within plus or minus the gure given.Furthermore, I have found that the combined crosssectional area of theports ZI leading from the ,5

bore should be greater than that of the crosssectional area of the boreand preferably this ratio is 1.5 so that the air may be rapidly eX-hausted. Similarly, it is desirable to have the combined volumes of theoutlets 23 greater than the cross-sectional areas of the annular groove22, and this ratio is preferably 1.5. When these ratios are maintained,the air is exhausted rapidly enough to prevent cushioning of the hammerblow. Thus, the eciency of the hammer is at a maximum and pounding ofthe piston against the cylinder end is prevented.

Although I have described but one form of the invention it is apparentthat other forms might be adopted, all falling Within the scope of theclaims which follow.

I claim:

l. A pneumatic hammer comprising a barrel member having a bore thereinand a cylinder at the inner end of the bore extending coaxially of thebore and being of greater diameter than the bore, said cylinder beingclosed at the end opposite the bore; a hammer piston in the bore andcylinder, said piston having a head closely tting the walls of thecylinder and a shank closely tting the Walls of the bore, said pistonbeing adapted to reciprocate in the barrel member to produce hammerstrokes; an air inlet passage opening into the cylinder at a pointspaced from the closed end of the cylinder whereby the piston head mayreciprocate in the cylinder Without closing said opening more thanmomentarily, said piston having a longitudinal bore therein extendingfrom the end of the piston head surface facing the closed end of thecylinder to a point in the shank; air ports leading from the inner endof said longitudinal bore to the side surface of the shank portion ofthe piston, said ports in the side surface of said shank being locatedto be exposed to the interior of the cylinder when the piston approachesone extremity of its stroke in the direction of the closed end of thecylinder and to be closed by the Walls of the bore when the piston isintermediate the extremities of its stroke; anA exhaust passage leadingfrom said bore and consisting of an annular groove in the walls of saidbore and having one or more outlet passages extending from the groove tothe atmosphere suflicient to exhaust said air through the piston exhaustport, said groove being located to be in registration with the openingin the side surface of said piston shank and being of approximately thesame longitudinal length as said opening When the piston is in saidopposite extremity of its stroke.

2. A pneumatic hammer of the character defined in claim 1 in which theair ports of the piston are divergently shaped from the inner end of thebore to the side surface of the shank portion of the piston in order toexhaust the air through these ports rapidly.

JACK E. TERRY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 666,757 Johnson Jan. 29, 1901805,222 Murphy Nov. 21, 1905 1,440,082 Inslee Dec. 26, 1922

